For various reasons crops sometimes are lying so close to the ground that it is difficult to cut them with a conventional harvest header. Some crops are inherently short, while others may be taller, but are prone to fall down when they reach maturity. Heavy rain or hail can also cause crop to be lying close to the ground at harvest time. Such a crop where relatively tall crop plants fall over close to the ground is commonly called a lodged crop.
Typically the knife on cutting headers comprises a knife bar extending along the front lower edge of the header, with a plurality of triangular knife sections attached to the bar such that the apex of the triangle extends forward from the bar. The exposed side edges of the knife sections are sharpened. Guards are attached to the front lower edge of the header and serve to protect the knife sections from breakage when contacting stones and like obstructions. The guards comprise pointed guard fingers extending forward, and the knife moves back and forth along the edge of the header in a slot cut laterally through the guard fingers. In addition to protecting the knife, the guard fingers also enable the knife sections to cut the crop. As the knife section moves back and forth it pushes crop against the sides of those portions of the guard finger that are above and below the slot, shearing the crop stalks.
A conventional knife is a few inches above the ground when the header is in its lowest position, such that very short or downed crop material will pass under the knife and be lost. Many different kinds of “crop lifters”, as they have come to be known, have been developed over the last century and more. Typically these crop lifters are attached to the header and/or the forward extending point of the guard finger, and provide an arm of various designs that rides along the ground ahead of the knife. A lifting finger extends at a shallow angle from the front of the arm back and over the knife. As the header moves down the field, the arm rides along the ground and under the downed crop stalks, which then are lifted and pass over the lifting finger to the knife, where they are cut and continue moving onto the header from where they can be passed to the harvester, swatter table, or the like.
U.S. Pat. Nos. 700,029 and 791,022 to Gatermann, U.S. Pat. No. 2,734,332 to Fisher, U.S. Pat. No. 2,892,298 to Chaney, U.S. Pat. No. 2,960,814 to Babcock, and Canadian Patent Number 407,654 to Young disclose a crop lifter that is pivotally attached to the header so as to be able to move up and down to follow the ground. The Babcock and Fisher devices float on the ground, while the others are biased toward the ground by springs. U.S. Pat. No. 4,120,138 to Schumacher illustrates a crop lifter that is fixed to the header instead of pivoting, but is made of spring steel so that same may move up and down to follow the ground.
U.S. Pat. No. 7,650,738 to Dietrich discloses a crop lifter with a bore member that is secured to a guard finger. The bore member defines a bore and the lifting finger extends through the bore such that a forward end thereof extends downward and forward from the bore member at a shallow angle to pass under and raise the crop stalks, and the rearward portion of the lifting finger extends rearward from the bore member and upward at the same shallow angle to a rear end above and rearward of the knife. The shallow angle is fixed at a desired angle that suits the conditions being encountered and can be adjusted.
Once cut, it is most desirable for efficient operation of the harvester mechanisms to deliver the stalks in a smooth orderly now from the knife to a feeding mechanism that conveys the stalks up into the harvester mechanism. Draper type cutting headers have right and left wide conveyor belts that move along the header table perpendicular to the operating travel direction with front edges thereof just behind the knife. The cut crop stalks fall onto the belts and are carried to a middle conveyor belt moving rearward that receives the stalks and carries them rearward into a feeder mechanism that moves them into the harvester mechanism. When cutting upright crop stalks, the stalks fall onto the belts generally parallel to each other, with the heads at the top ends of the stalks together on the inner side of the belts, and are moved smoothly to the middle conveyor belt and head first into the feeder mechanism.
In contrast, auger type cutting headers for harvesters have a large diameter auger extending from one end of the header to the other perpendicular to the operating travel direction. Right hand and left hand auger flighting on corresponding end portions of the auger carry the cut crop stalks to a feeder mechanism generally in the middle of the table. Fingers on the middle portion of the auger grab the stalks and push them rearward into the feeder mechanism. In the auger type header there is some distance between the knife and the outer edges of the auger fighting. When cutting upright crop stalks, the stalks fall against the flighting as they are cut and are moved smoothly to the feeder mechanism with the heads at the top ends of the stalks falling toward the center so that the stalks enter the feeding mechanism head first.
When the crop stalks are tying down close to the ground however, crop lifter are often required to raise the stalks above the knife so same can be cut. These conventional crop lifters only raise the stalks a short distance above the knife, such that they when cut they are still generally lying down. The cut stalks can have heads pointed in all directions and, in an auger type header, once cut they must slide rearward across a width of header table before contacting the auger flighting under generally the rotational center of the auger where outer edges of the fighting are located close to the header table. In some conditions the stalks do not flow smoothly over the table to the auger, but bunch up and move to the auger in lumps, reducing the efficiency of the harvester.
In both auger and draper type headers, with conventional crop lifters raising crop stalks that are lying down, the stalks enter the feeder mechanism oriented in all directions, some sideways, some cut end first, and with only a portion in the desirable head first orientation. Harvester efficiency is reduced compared to a smooth head first flow of crop stalks.